In recent years, piezoelectric vibrators using crystals or the like have been used in mobile phones or personal digital assistants, as a time source or a timing source such as a control signal, or a reference signal source and the like. Various types of piezoelectric vibrators are provided, but as one of them, an SMD type piezoelectric vibrator is known. As this type of piezoelectric vibrator, generally, a three layer structure type, in which a piezoelectric substrate formed with a piezoelectric vibrating reed are bonded so as to be interposed from above and below by a base substrate and a lid substrate, is known. In this case, the piezoelectric vibrating reed is accommodated in a cavity (sealing chamber) formed between the base substrate and the lid substrate.
Furthermore, recently, a two layer structure type is also developed instead of the three layer structure type. This type of piezoelectric vibrator has the two layer structure, in which the base substrate and the lid substrate are directly bonded to each other and the piezoelectric vibrating reed is accommodated within the cavity formed between both substrates. The piezoelectric vibrator of a two layer structure is excellent in that thinning can be promoted as compared to the three layer structure and is preferentially used.
However, it is generally desirable with piezoelectric vibrators that the equivalent resistance values (effective resistance value, Re) of the piezoelectric vibrator are further suppressed to a lower level. Since piezoelectric vibrators with lower equivalent resistance values can vibrate the piezoelectric vibrating reed using less voltage, they are more energy efficient piezoelectric vibrators.
As one of the common methods of suppressing the equivalent resistance value, a method of making a portion within a cavity closer to a vacuum is known. Furthermore, as a method of making the inner portion of the cavity closer to a vacuum, a method of accommodating (gettering) a getter material which is a metallic film in the cavity and irradiating a laser or the like from the outside to heat and activate the getter material is known (see Patent Citation 1).
According to this method, since, the gas mainly consisted of oxygen in the cavity can be absorbed by the getter material entering the activation state by a chemical reaction, the inner portion of the cavity can be made closer to a vacuum. In addition, the getter material consists of aluminum, titanium, zirconium or an alloy thereof, but, particularly, aluminum is preferentially used in that it absorbs the gas in the cavity when being heated and can effectively improve a degree of vacuum (the gettering efficiency thereof is high).    [Patent Citation 1] JP-A-2003-142976
However, when aluminum is used as the getter material, there is a concern that a decline in quality of the piezoelectric vibrator and a change in property may be caused. That is, aluminum has a property of being easily chemically eroded by a medium such as moisture. For that reason, when the piezoelectric vibrator is under high humidity, there is a chance that the getter material is corroded by the humidity. When corrosion occurs, the surface of the getter material can be radically etched or corrosion products may appear on the surface. For that reason, there is a concern that a decline in quality is caused, and the vibration operation of the piezoelectric vibrating reed is affected, and a change in property is caused.
The present invention is made in view of the above circumstances, and an object thereof is to provide a piezoelectric vibrator that can exhibit the high gettering effect and does not cause quality decline or property change by the influence of humidity. Furthermore, it is possible to provide a piezoelectric manufacturing method to manufacture the piezoelectric vibrator, and to provide an oscillator, electronic equipment and a radio-controlled timepiece having the piezoelectric vibrator.